In an electronic device such as a mobile phone, temperature inside the device may increase locally due to heat generated by a heating element mounted on a board. In order to suppress such a rise in the temperature, it is a known practice to employ a heat dissipation structure using a thermal diffusion sheet.
As a technique related to the heat dissipation structure using the thermal diffusion sheet, there is a conventional technique in which a heat sink formed by laminating adhesive layers and thermal diffusion sheets alternately is placed in contact with a heating element. In another conventional technique, an opening is formed in an adhesive layer at a region corresponding to a heating element, and an air layer serving as a heat insulating layer is formed between a member opposed to the heating element via the opening, and a thermal diffusion sheet laminated on the adhesive layer. An example of the related conventional techniques is disclosed in Japanese Laid-open Patent Publication No. 2012-160503.